Can't open a FileList in one of my projects

Hi,

in a 4.5-13680 image under Win 7 I can't open a FileList in one of the
five projects I have in this image. (See attached MNU).
In the other four projects the FileList  works. As it's the last project
I created in that image I tried opening another project. In the new one
the FileList  also works.

I really have no clue what might cause this. Attaching an image and
changes to a mantis bug seems inappropriate :-))

Any hints?

Cheers

Herbert